Transistors, Semiconductor Constructions, and Methods of Forming Semiconductor Constructions

ABSTRACT

Some embodiments include a transistor having a first electrically conductive gate portion along a first segment of a channel region and a second electrically conductive gate portion along a second segment of the channel region. The second electrically conductive gate portion is a different composition than the first electrically conductive gate portion. Some embodiments include a method of forming a semiconductor construction. First semiconductor material and metal-containing material are formed over a NAND string. An opening is formed through the metal-containing material and the first semiconductor material, and is lined with gate dielectric. Second semiconductor material is provided within the opening to form a channel region of a transistor. The transistor is a select device electrically coupled to the NAND string.

TECHNICAL FIELD

Transistors, semiconductor constructions, and methods of formingsemiconductor constructions.

BACKGROUND

A field effect transistor (FET) is a three-channel circuit devicecomprising a gated channel region between a source and a drain. FETshave numerous applications in integrated circuitry. For instance, FETsmay be utilized in memory; and may be, for example, utilized incombination with capacitors to form dynamic random access memory (DRAM)unit cells; utilized as select devices relative to NAND strings;utilized as select devices for controlling access to programmablemetallization cells (PMCs); etc. Additionally, or alternatively, FETsmay be utilized in logic.

There are continuing goals to develop improved FETs and improved methodsof forming FETs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-4 are diagrammatic cross-sectional side views of exampleembodiment transistors.

FIGS. 5 and 6 are a diagrammatic cross-sectional side view and adiagrammatic top view, respectively, of a portion of a semiconductorconstruction illustrating an example embodiment vertical transistorconfigured as a select device coupled to a vertical NAND string. The topview of FIG. 6 is along a line 6-6 of FIG. 5.

FIGS. 7 and 8 are a diagrammatic cross-sectional side view and adiagrammatic top view, respectively, of a portion of a semiconductorconstruction illustrating another example embodiment vertical transistorconfigured as a select device coupled to a vertical NAND string. The topview of FIG. 8 is along a line 8-8 of FIG. 7.

FIGS. 9-13 are diagrammatic cross-sectional side views of a portion of asemiconductor construction at various process stages of an exampleembodiment method of forming an example embodiment vertical transistor.

FIG. 14 is a diagrammatic cross-sectional side view of a portion of asemiconductor construction at a process stage of another exampleembodiment method of forming an example embodiment vertical transistor.The process stage of FIG. 14 may follow that of FIG. 12 in someembodiments.

FIGS. 15-18 are diagrammatic cross-sectional side views of a portion ofa semiconductor construction at various process stages of anotherexample embodiment method of forming an example embodiment verticaltransistor. The process stage of FIG. 15 may follow that of FIG. 10 insome embodiments.

FIG. 19 is a diagrammatic cross-sectional side view of a portion of asemiconductor construction at a process stage of another exampleembodiment method of forming an example embodiment vertical transistor.The process stage of FIG. 19 may follow that of FIG. 17 in someembodiments.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

In some embodiments, new FETs are configured to comprise gates having atleast two different conductive materials which are each along adifferent segment of a channel region. In some embodiments, such FETsare configured as vertical devices, and are utilized as select deviceswhich are electrically coupled to vertical NAND strings. Exampleembodiments are described below with reference to FIGS. 1-19.

Referring to FIG. 1, a semiconductor construction 10 comprises a base 12supporting an example embodiment transistor 14.

The base 12 may comprise semiconductor material, and in some embodimentsmay comprise, consist essentially of, or consist of monocrystallinesilicon. In some embodiments, base 12 may be considered to comprise asemiconductor substrate. The term “semiconductor substrate” means anyconstruction comprising semiconductive material, including, but notlimited to, bulk semiconductive materials such as a semiconductive wafer(either alone or in assemblies comprising other materials), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure, including, but not limited to, the semiconductor substratesdescribed above. In some embodiments, base 12 may correspond to asemiconductor substrate containing one or more materials associated withintegrated circuit fabrication. Some of the materials may be under theshown region of base 12 and/or may be laterally adjacent the shownregion of base 12; and may correspond to, for example, one or more ofrefractory metal materials, barrier materials, diffusion materials,insulator materials, etc.

The transistor 14 comprises a pair of conductively-doped source/drainregions 16 and 18 extending into base 12. The source/drain regions maybe majority n-type doped in some embodiments, and may be majority p-typedoped in other embodiments.

A channel region 20 is within base 12 between the source/drain regions16 and 18. Such channel region may be doped with appropriate dopant.

A gate dielectric 22 extends across the channel region 20, and in theshown embodiment also extends across the source/drain regions 16 and 18.The gate dielectric is directly against the channel region. The gatedielectric may comprise any suitable composition or combination ofcompositions; and in some embodiments may comprise, consist essentiallyof, or consist of one or more of silicon dioxide, silicon nitride,aluminum oxide, hafnium oxide, zirconium oxide, etc. Although the gatedielectric is shown as a single homogeneous electrically insulativecomposition, in other embodiments the gate dielectric may comprise twoor more discrete electrically insulative compositions; such as, forexample, two or more discrete compositions stacked one on top ofanother.

A gate 24 is over the gate dielectric 22. The gate 24 comprises a firstelectrically conductive gate portion 25 and a second electricallyconductive gate portion 27; with portions 25 and 27 comprising materials26 and 28, respectively. The portions 25 and 27 are directly against oneanother in a side-by-side arrangement over the channel region.

The materials 26 and 28 are of different compositions relative to oneanother, and may comprise any suitable compositions. In some exampleembodiments, one of the materials 26 and 28 comprises, consistsessentially of, or consists of conductively-doped semiconductor material(for instance, conductively-doped silicon, conductively-doped germanium,etc.); and the other comprises, consists essentially of, or consists ofmetal (for instance, comprises elemental metal, metal nitride, metalsilicide, etc.). In some embodiments, the portion 26 may consist ofn-type doped silicon (e.g., n-type doped polysilicon) or p-type dopedsilicon (e.g., p-type doped polysilicon); and the portion 28 maycomprise, consist essentially of, or consist of titanium nitride ortungsten silicide.

The channel region 20 may be considered to comprise a first segment 30and a second segment 32. The portions 25 and 27 of gate 24 are along thefirst and second segments 30 and 32 of the channel region, respectively;and are spaced from such segments by gate dielectric 22. In the shownembodiment, the first and second portions 25 and 27 of gate 24 aredirectly against gate dielectric 22. In other embodiments, such portionsmay be spaced from the gate dielectric by an intervening electricallyconductive material (as discussed below with reference to FIGS. 3 and4).

The source and drain regions 16 and 18 are shown to be electricallycoupled to circuitry 34 and 36, respectively, and the gate is shown tobe electrically coupled to circuitry 38. The transistor 14 is a FET. Inoperation gate 24 can be utilized to impart an electric field to thechannel region 20 to alter conductivity through the channel region, andto thereby gatedly couple source/drain regions 16 and 18 to one another.

One of the source/drain regions 16 and 18 is a source region and theother is a drain region. In some example embodiments, the gate portions25 and 27 may be a semiconductor-containing gate portion and ametal-containing gate portion, respectively, and the source/drainregions 16 and 18 may be arranged to put the drain region adjacent themetal-containing gate portion. In other example embodiments in which thegate portions 25 and 27 are a semiconductor-containing gate portion anda metal-containing gate portion, respectively, the source/drain regions16 and 18 may be arranged to put the drain region adjacent to thesemiconductor-containing gate portion.

The example embodiment of FIG. 1 comprises a gate having two discreteportions. In other embodiments, a gate may comprise more than twodiscrete portions. For instance, FIG. 2 shows a construction 10 aillustrating a transistor 14 a having a gate 24 a with three discreteportions 25, 27 and 39 which comprise materials 26, 28 and 40,respectively. In some embodiments, the portions 25 and 39 may besemiconductor-containing portions, and the portion 27 may be ametal-containing portion. In other embodiments, the portions 25 and 39may be metal-containing portions, and the portion 27 may be asemiconductor-containing portion. In some embodiments, the materials 26and 40 of portions 25 and 39 may comprise the same composition as oneanother, and in other embodiments the materials 26 and 40 may be ofdifferent compositions relative to one another.

The channel region 20 of FIG. 2 may be considered to comprise a thirdsegment 42, in addition to the first and second segments 30 and 32; withthe portion 39 of gate 24 a being along such third segment of thechannel region, and being spaced from the third segment by gatedielectric 22.

In some embodiments, the portions of the transistor gate may be spacedfrom gate dielectric by electrically conductive material. For instance,FIG. 3 shows a construction 10 b illustrating a transistor 14 b having agate 24 spaced from gate dielectric 22 by an electrically conductivematerial 44. In some embodiments, the electrically conductive material44 may comprise, consist essentially of, or consist ofconductively-doped semiconductor material (for instance, one or more ofconductively-doped silicon, conductively-doped germanium, etc.). Theelectrically conductive material 44 may be thin in some embodiments toenable good electrical coupling between portions 25 and 27 of gate 24with the underlying segments 30 and 32 of channel region 20. Forinstance, in some embodiments material 44 may have a thickness of lessthan or equal to about 100 Å; such as, for example, a thickness within arange of from about 5 Å to about 100 Å.

The example embodiment of FIG. 3 comprises a gate having two discreteportions, but in other embodiments a gate may comprise more than twodiscrete portions. FIG. 4 shows a construction 10 c illustrating atransistor 14 c having a gate 24 a of the type described above withreference to FIG. 2, (i.e., a gate having three discrete portions 25, 27and 39) utilized in combination with the electrically conductivematerial 44 between the gate and the gate dielectric 22.

In some example embodiments, transistors analogous to those describedabove with reference to FIGS. 1-4 may be utilized in NAND memory arraysas select devices coupling to NAND strings. FIG. 5 shows a semiconductorconstruction 10 d having a NAND string 50 supported by a semiconductorbase 12. The NAND string extends vertically over an upper surface of thebase. Specifically, the base has a substantially horizontal primarysurface 13 (e.g., an upper surface of a semiconductor wafercorresponding to base 12 in some embodiments) extending along adirection of an axis 5, and the NAND string extends along a direction ofan axis 7 which is substantially orthogonal to the axis 5.

The NAND string comprises multiple levels of memory cells 51 arrangedone on top of the other over base 12. One of such memory cells is shownin FIG. 5 to comprise a charge-storage material 52 spaced from a controlgate material 53 by dielectric material 54. The charge-storage materialmay comprise any suitable composition or combination of compositions. Insome embodiments, the charge-storage material may be configured as afloating gate, and accordingly may comprise silicon. In otherembodiments, the charge-storage material may be configured as a chargetrap, and accordingly may comprise silicon nitride, nanodots, etc. Thedielectric material 54 may comprise any suitable composition orcombination of compositions, including, for example, one or more ofvarious oxides (for instance, silicon dioxide, aluminum oxide, hafniumoxide, zirconium oxide, etc.). The control gate material 53 may compriseany suitable composition or combination of compositions; and in someembodiments may comprise, consist essentially of, or consist ofconductively-doped silicon.

The NAND string 50 comprises a NAND string channel material 55. Suchchannel material may comprise any suitable composition or combination ofcompositions; and in some embodiments may comprise, consist essentiallyof, or consist of appropriately-doped silicon. The gate 51 is adjacentthe NAND string channel material 55, and there would be a gatedielectric (not shown) between the charge-storage material 52 and thechannel material 55.

The memory cell 51 may be representative of a large number of memorycells incorporated into a string of memory cells. For instance, in someembodiments the string of memory cells may comprise 8 cells, 16 cells,32 cells, 64 cells, etc.

A transistor 60 is over the NAND string and electrically coupled withthe NAND string channel material 55. The transistor 60 is analogous tothe transistor 14 of FIG. 1, but is a vertical device rather than theplanar device shown in FIG. 1. Specifically, transistor 60 comprises achannel 20 which is elongated along a vertical direction (i.e., adirection of axis 7) rather than along a horizontal direction.

The transistor 60, like the transistor 14 of FIG. 1, has a gate 24comprising two portions 25 and 27, and such gate is separated from thechannel region 20 by gate dielectric 22. The channel region 20 is withina semiconductor material 62, which in some embodiments may comprise,consist essentially of, or consist of appropriately-doped silicon. Thematerials 62 and 55 may be the same material as one another in someembodiments, and may, for example, be comprised by a single pillar ofpolysilicon.

The gate portions 25 and 27 are along vertically-offset segments 30 and32 of channel region 20, respectively.

Source/drain regions 16 and 18 (shown in FIG. 1, and not shown in FIG.5) may be formed within material 62 on opposing sides of channel region20 from one another. Alternatively, an entirety of material 62 may beuniformly doped (and such doping may also extend into or entirelythrough, material 55 in some embodiments). In other example embodiments,a region analogous to source/drain region 18 may be formed withinmaterial 62 while the rest of material 62 remains uniformly doped.

The construction 10 d comprises a first electrically insulative material64 under gate portion 25, and a second electrically insulative material66 over gate portion 27. The electrically insulative material 64 may beutilized for electrical isolation between gate portion 25 and othermaterials underlying such gate portion, such as, for example, materialsassociated with NAND string 50 Similarly, the electrically insulativematerial 66 may be utilized for electrical isolation between gateportion 27 and other materials overlying such gate portion. In someexample embodiments, electrically insulative material 64 may comprise,consist essentially of, or consist of silicon dioxide; and electricallyinsulative material 66 may comprise, consist essentially of, or consistof silicon nitride.

In some embodiments, material 26 of gate portion 25 may consist ofconductively-doped silicon (for instance, n-type doped silicon) having athickness within a range of from about 50 nm to about 200 nm; andmaterial 28 of gate portion 27 may consist of tungsten silicide ortitanium nitride having a thickness within a range of from about 10 nmto about 100 nm. In such embodiments, the relative thicknesses of theportions 25 and 27 may be tailored to achieve desired properties. Insome embodiments, the semiconductor-containing gate portion 25 may be atleast about 50% thicker than the metal-containing gate portion 27. Insome embodiments, the metal-containing portion of gate 24 may be underthe semiconductor-containing portion, and in other embodiments may beover the semiconductor-containing portion.

FIG. 6 shows a top view of construction 10 d, and shows that the channelregion 62 may be configured as a pillar extending upwardly through gateportions 25 and 27. Such pillar is laterally surrounded by the gatedielectric 22. The portions 25 and 27 of gate 24 entirely laterallysurround such pillar-shaped channel region in the shown embodiment.

FIGS. 5 and 6 show a vertical device analogous to the transistorconfiguration of FIG. 1. In other embodiments, vertical devices may beformed to be analogous to one or more of the transistor configurationsof FIGS. 2-4. For instance, FIGS. 7 and 8 show a construction 10 esimilar to that of FIGS. 5 and 6, but utilizing a transistor 70 based onthe configuration of FIG. 3, rather than the transistor based on theconfiguration of FIG. 1. Accordingly, the construction 10 e of FIGS. 7and 8 comprises the electrically conductive material 44 between thedielectric material 22 and the gate portions 25 and 27.

Although individual transistors and NAND strings are shown in FIGS. 5-8,such individual transistors and NAND strings may be representative of alarge number of substantially identical devices formed across asemiconductor construction. For instance, the transistors and NANDstrings of FIGS. 5-8 may be representative of a large number ofsubstantially identical devices incorporated into a NAND memory array.

The vertically-oriented transistors of FIGS. 5 and 7 are shown utilizedin conjunction with NAND strings. In other embodiments, analogousvertically-oriented transistors may be utilized in other applications,such as, for example, DRAM and/or logic.

The constructions of FIGS. 1-8 may be considered to correspond to hybridgates, in that the gates comprise two or more different materialsincorporated therein. Prior art gate constructions utilized multiplegate materials stacked over one another so that all of the gatematerials were over a common segment of a channel region, (example priorart devices utilizing both metal-containing material andsemiconductor-containing material in transistor gates are metal-strappeddevices). In contrast to prior art devices, the constructions of FIGS.1-8 have each of the separate materials of the gate over a separatesegment of the channel. Such can provide advantages in tailoring thegates for applications associated with highly integrated circuitry. Forinstance, the embodiments of FIGS. 5-8 may utilize hybrid gates invertically-oriented select drain devices as part of NAND memory arrays.Such gates may enable higher threshold voltage and reducedresistance-capacitance (RC) as compared to prior art devices. Further,the footprint of the devices of FIGS. 5-8 may be reduced relative toconventional metal-strapped devices due to the elimination of thestrapping constituent.

The constructions described above with reference to FIGS. 1-8 may beformed with any suitable processing. Some example methods are describedbelow with reference to FIGS. 9-19.

Referring to FIG. 9, a construction 10 f is shown to comprise avertically-extending NAND string 50 formed over a base 12 (the NANDstring of FIG. 9 is shown more diagrammatically than the NAND strings ofFIGS. 5 and 7, but may comprise a similar configuration as the NANDstrings of FIGS. 5 and 7).

A stack 72 is formed over the NAND string. The stack comprises thematerials 64, 26, 28 and 66. In some embodiments such materials may bereferred to as a first electrically insulative material, firstsemiconductor material, metal-containing material, and secondelectrically insulative material, respectively. The stack 72 may beformed by forming the various materials 64, 26, 28 and 66 on top of oneanother with any suitable processing including, for example, one or moreof atomic layer deposition (ALD) and chemical vapor deposition (CVD) andphysical vapor deposition (PVD).

Referring to FIG. 10, an opening 74 is formed to extend through thematerials 26, 28 and 66, and to an upper surface of electricallyinsulative material 64. Such opening may be formed with any suitableprocessing. For instance, in some embodiments a mask (for instance, aphotolithographically-patterned photoresist mask and/or a mask formed bypitch-modification methodologies) may be formed over stack 72 to definea location of opening 74; one or more etches may be utilized to transfera pattern from the mask into materials 26, 28 and 66 to thereby formopening 74; and then the mask may be removed to leave the constructionshown in FIG. 10. In some embodiments, the mask may be utilized incombination with carbon and/or antireflective material (not shown).

The opening 74 has sidewalls 73 along materials 26, 28 and 66, and has abottom 75 along material 64. Although the opening appears to have twoseparate sidewalls in the cross-section of view of FIG. 10, in someembodiments the sidewalls may merge to form a single sidewall. Forinstance, the opening 74 may have a circular shape, or other closedshape, when viewed from above (for instance, may have a shape analogousto the circular shape shown in the top view of FIG. 6).

Referring to FIG. 11, gate dielectric 22 is formed over stack 72 andwithin opening 74, and then a spacer material 76 is formed over the gatedielectric 22. The gate dielectric and spacer material may be formedwith any suitable processing, including, for example, one or more ofALD, CVD and PVD. The gate dielectric 22 and spacer material 76 extendalong the sidewalls 73 and bottom 75 of opening 74, and only partiallyfill such opening.

The spacer material 76 may comprise any suitable composition. In someembodiments, the spacer material is ultimately incorporated intosemiconductor material utilized for a channel region, and thus maycomprise a same composition as the rest of the semiconductor material(e.g., in some embodiments the spacer material may comprise, consistessentially of, or consist of silicon). In such embodiments, the spacermaterial may be referred to as a semiconductor material liner. In otherembodiments, spacer material 76 may be a sacrificial material, and thusmay comprise any composition which may be selectively removed relativeto other compositions of construction 10 f.

Referring to FIG. 12, the materials 22 and 76 are subjected toanisotropic etching. Such removes materials 22 and 76 from over a topsurface of material 66, and exposes material 64 along the bottom ofopening 74. In the shown embodiment, the etching has continued throughmaterial 64 to punch an opening 78 through material 64. In someembodiments, openings 74 and 78 may be referred to as a first openingand a second opening, respectively. In some embodiments, spacer material76 may be considered to be utilized as a mask during formation ofopening 78.

The anisotropic etching of the spacer material 76 may be considered topattern such material into spacers 80 along sidewalls of opening 74.Although there appear to be two spacers 80 in the cross-sectional viewof FIG. 12, in some embodiments such spacers may be comprised by asingle spacer that forms an annular ring within a circular-shapedopening 74.

Referring to FIG. 13, semiconductor material 62 is formed within thefirst and second openings 74 and 78. In some embodiments, one or both ofthe source/drain regions 16 and 18 (shown in FIG. 1, but not in FIG. 13)may be formed in material 62, and in other embodiments the entirety ofmaterial 62 may be uniformly doped. The materials 62 and 76 may have asame composition as one another, and accordingly the construction ofFIG. 13 may comprise a transistor 60 identical to the transistordescribed above with reference to FIG. 5. In some embodiments, thesemiconductor material 62 may be referred to as a second semiconductormaterial to distinguish it from the first semiconductor material 26.

In some embodiments, spacer material 76 may be a sacrificial material,and may be removed prior to formation of semiconductor material 62. FIG.14 shows a construction 10 g at a processing stage subsequent to that ofFIG. 12 in accordance with an embodiment in which spacer material 76 isremoved prior to formation of semiconductor material 62.

In some embodiments, the electrically conductive material 44 (FIGS. 3,4, 7 and 8) may be formed prior to forming dielectric material 22. Forinstance, FIG. 15 shows a construction 10 h at a processing stage whichmay be subsequent to that of FIG. 10 in some embodiments, (in the shownembodiment, the opening 74 of FIG. 15 is wider than that of FIG. 10 inorder to improve legibility of the drawings as additional materials areformed in the opening in subsequent steps). Material 44 has been formedas a conductive liner along sidewalls of opening 74. Such conductiveliner may be formed by any suitable method. For example, material 44 maybe formed across an upper surface of stack 72 and along the sidewalls 73and bottom 75 of opening 74 utilizing one or more of ALD, PVD and CVD.Subsequently, material 44 may be subjected to anisotropic etching toform the configuration of FIG. 15.

Referring to FIG. 16, gate dielectric 22 and spacer material 76 areformed across stack 72 and within opening 74 utilizing processinganalogous to that described above with reference to FIG. 11.

Referring to FIG. 17, materials 22 and 76 are anisotropically etchedwith processing analogous to that described above with reference to FIG.12, and then the second opening 78 is punched through material 64.Although material 44 is shown to be anisotropically etched prior toforming materials 22 and 76 within the opening 74, in other embodimentsthe materials 22 and 76 may be formed over material 44 without firstanisotropically etching material 44. In such other embodiments, material44 may be etched with materials 22 and 76 at the processing stage ofFIG. 17 to pattern the location for the opening 78.

Referring to FIG. 18, semiconductor material 62 is formed withinopenings 74 and 78. In some embodiments, materials 62 and 76 may be asame composition as one another so that such materials merge to form asingle material, and thus the construction of FIG. 18 may be identicalto that described above with reference to FIG. 7.

In some embodiments, material 76 may be a sacrificial material, and maybe removed prior to formation of semiconductor material 62. FIG. 19shows a construction 10 i at a processing stage subsequent to that ofFIG. 17 in accordance with an embodiment in which spacer material 76 isremoved prior to formation of semiconductor material 62.

In some embodiments, the processing of FIGS. 9-19 may be utilized toform a plurality of substantially identical devices which areincorporated into a NAND memory array.

The transistors, arrays and constructions discussed above may beincorporated into electronic systems. Such electronic systems may beused in, for example, memory modules, device drivers, power modules,communication modems, processor modules, and application-specificmodules, and may include multilayer, multichip modules. The electronicsystems may be any of a broad range of systems, such as, for example,clocks, televisions, cell phones, personal computers, automobiles,industrial control systems, aircraft, etc.

The terms “dielectric” and “electrically insulative” are both utilizedto describe materials having insulative electrical properties. Bothterms are considered synonymous in this disclosure. The utilization ofthe term “dielectric” in some instances, and the term “electricallyinsulative” in other instances, is to provide language variation withinthis disclosure to simplify antecedent basis within the claims thatfollow, and is not utilized to indicate any significant chemical orelectrical differences.

The particular orientation of the various embodiments in the drawings isfor illustrative purposes only, and the embodiments may be rotatedrelative to the shown orientations in some applications. The descriptionprovided herein, and the claims that follow, pertain to any structuresthat have the described relationships between various features,regardless of whether the structures are in the particular orientationof the drawings, or are rotated relative to such orientation.

The cross-sectional views of the accompanying illustrations only showfeatures within the planes of the cross-sections, and do not showmaterials behind the planes of the cross-sections in order to simplifythe drawings.

When a structure is referred to above as being “on” or “against” anotherstructure, it can be directly on the other structure or interveningstructures may also be present. In contrast, when a structure isreferred to as being “directly on” or “directly against” anotherstructure, there are no intervening structures present. When a structureis referred to as being “connected” or “coupled” to another structure,it can be directly connected or coupled to the other structure, orintervening structures may be present. In contrast, when a structure isreferred to as being “directly connected” or “directly coupled” toanother structure, there are no intervening structures present.

In some embodiments, the invention includes a transistor. The transistorincludes a channel region, gate dielectric directly against the channelregion, and a first conductive gate portion along a first segment of thechannel region. The first conductive gate portion is spaced from saidfirst segment by at least the gate dielectric. The transistor alsoincludes a second conductive gate portion along a second segment of thechannel region, and spaced from said second segment by at least the gatedielectric. The second segment is adjacent to the first segment. Thesecond conductive gate portion comprises a different composition fromthe first conductive gate portion.

In some embodiments, the invention includes a semiconductorconstruction. The construction includes a channel region. Gatedielectric is directly against the channel region, and asemiconductor-containing gate portion is along a first segment of thechannel region and spaced from said first segment by at least the gatedielectric. The semiconductor-containing gate portion consists ofconductively-doped semiconductor material. A metal-containing gate isalong a second segment of the channel region and spaced from said secondsegment by at least the gate dielectric. The second segment is adjacentto the first segment. The semiconductor-containing gate portion,metal-containing gate portion, dielectric material and channel regioncomprise a transistor.

In some embodiments, the invention includes a method of forming asemiconductor construction. A vertically-extending NAND string is formedover a substantially horizontal primary surface of a base. The NANDstring has a vertically-extending NAND string channel region. Anelectrically insulative material is formed over the NAND string channelregion. A first semiconductor material is formed over the electricallyinsulative material. Metal-containing material is formed over the firstsemiconductor material. A first opening is formed to extend through themetal-containing material and the first semiconductor material to theelectrically insulative material. A gate dielectric is formed alongsidewalls and a bottom of the first opening. A second opening is formedthrough the gate dielectric at the bottom of the first opening andthrough the electrically insulative material. Second semiconductormaterial is formed within the first and second openings. A portion ofthe second semiconductor material within the first opening is spacedfrom the first semiconductor material and the metal-containing materialby at least the gate dielectric and is a transistor channel region.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

1-20. (canceled)
 21. A method of forming a semiconductor construction,comprising: forming a vertically-extending NAND string over asubstantially horizontal primary surface of a base; the NAND stringhaving a vertically-extending NAND string channel region; forming anelectrically insulative material over the NAND string channel region;forming a first semiconductor material over the electrically insulativematerial; forming metal-containing material over the first semiconductormaterial; forming a first opening to extend through the metal-containingmaterial and the first semiconductor material to the electricallyinsulative material; forming a gate dielectric along sidewalls and abottom of the first opening; forming a second opening through the gatedielectric at the bottom of the first opening and through theelectrically insulative material; and forming second semiconductormaterial within the first and second openings; a portion of the secondsemiconductor material within the first opening being spaced from thefirst semiconductor material and the metal-containing material by atleast the gate dielectric and being a transistor channel region.
 22. Themethod of claim 21 further comprising forming a semiconductor materialliner along sidewalls of the first opening prior to forming the gatedielectric.
 23. The method of claim 22 wherein the semiconductormaterial liner comprises silicon.
 24. The method of claim 21 furthercomprising forming an electrically conductive liner along sidewalls ofthe first opening prior to forming the gate dielectric.
 25. The methodof claim 24 wherein the liner comprises conductively-doped polysilicon.26. The method of claim 21 further comprising: forming spacer materialalong the gate dielectric within the first opening prior to forming thesecond opening; and utilizing the spacer material as a mask duringformation of the second opening.
 27. The method of claim 26 wherein thespacer material comprises semiconductor material and is incorporatedinto the transistor channel region.
 28. The method of claim 26 furthercomprising removing the spacer material prior to forming the secondsemiconductor material within the first and second openings.
 29. Themethod of claim 21 wherein the first semiconductor material comprisessilicon.
 30. The method of claim 21 wherein the metal-containingmaterial comprises titanium or tungsten.
 31. The method of claim 21wherein the metal-containing material comprises titanium nitride. 32.The method of claim 21 wherein the metal-containing material comprisestungsten silicide.
 33. A method of forming a semiconductor construction,comprising: providing a vertically-extending NAND string having avertically-extending NAND string channel region; forming an electricallyinsulative material over the NAND string channel region; forming asilicon-containing material over the electrically insulative material;forming metal-containing material over the silicon-containing material,the metal-containing material comprising metal nitride or metalsilicide; forming a first opening to extend through the metal-containingmaterial and the silicon-containing material to the electricallyinsulative material; forming a gate dielectric along sidewalls and abottom of the first opening; forming a second opening through the gatedielectric at the bottom of the first opening and through theelectrically insulative material; and forming semiconductor materialwithin the first and second openings; a portion of the semiconductormaterial within the first opening being spaced from thesilicon-containing material and the metal-containing material by atleast the gate dielectric and being a transistor channel region.